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Discussion Starter #1
With the autox season over, I'm reflecting on the cars performance this year trying to understand where I can improve the car or myself. I thought it would be beneficial to get some ideas and feedback from the group.

The Car -
987.1 (not a daily, but not a race car; primarily used for the AutoX)
19x8 235/35/19 PSS
19.95 265/35/19 PSS
Numeric Shift Cables
Numeric Short Shifter
Cargraphic Exhaust
Softronics 93 Oct Sport Chronos Flash
Tarret GT3 Front LCAs - Installed for increase caster (cup setting)
Pagid Orange (F/R)

Alignment -
Front:
Camber -1.8 (L/R)
Toe Out 1/32 (L/R) Total toe Out 1/16
Rear:
Camber -1.0 (L/R)
Toe In 1.32(L/R) Total Toe In 1/16

The first half of the season the car felt like it was pushing a lot. I also ended up chewing through my front tire's shoulders. I upgraded to the Tarret GT3 LCAs, gave it some more camber, and bought fresh rubber (PSS). The tires are now wearing very good now. I think the camber is perfect.

Following the upgrade to the front, the car went from pushing to rotating. Its nice and makes for an entertaining lap at the autox but I find myself having to wait for the car. Best described as: A period where I'm not on the brakes and not on the gas because the moment I touch the gas the rear immediately slides out.

I want to fix this problem for next year, because I think this is causing me to lose half a second. The thing is, my rear PS tires are on the wear bars. The tires are also 2 years old. I'm thinking of making a few changes to the rear. I'll definitely be adding a tiny bit of camber, I'm just over the shoulder in terms of wear. But what about the oversteer?

Do I:
1. Get new tires in 265, add some rear camber, and leave the rest alone?
2. Get new tires in 275, add some rear camber, and leave the rest alone?
3. Reduce front caster, get new tires in 265, and add some rear camber?
4. Reduce front caster, get new tires in 275, and add some rear camber?

Decisions decision.... And there is also the question that the rotation is fine and that I need to improve myself as a driver.

Lastly, I'm thinking of addressing rear tire spin. The car loves to spin the inside tire under steering input and throttle. I know this is a problem for this car. Especially on stock suspension, as the car does lean. I know some people get an LSD, and others get sway bars. Is there any thing else I can do to address this situation?

Thanks in advance!
Syeo86
 

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Several of the issues you mention could be improved by moving more toward a square tire setup. I also don't think the lifted inner wheel lift will get worse from it.

If money is available and this is important to you I would put adjustable suspension parts so that you can tweak settings on your own.
 

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Discussion Starter #3 (Edited)
Several of the issues you mention could be improved by moving more toward a square tire setup. I also don't think the lifted inner wheel lift will get worse from it.

If money is available and this is important to you I would put adjustable suspension parts so that you can tweak settings on your own.
More square? Can you explain a bit more?

As for adjustable suspension components, the money is available but I'm trying not to bump myself out of my Autox class. I know lowering the car will help with the wheel lift, sway bars might help too. But I'm almost sure that either will push me out of my class.

Also if a moderator can move this, I accidentally posted in the subforum.
 

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Discussion Starter #4
Thanks for that BTW.

I just spent the last 2 hours digging around square vs staggered.

I'm going to stick to staggered, probably run 275, and if the car is still oversteering I'll disconnect the rear sway. I have a feeling that should be more than enough adjustment.
 

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I don't think you can go actually square without losing more traction. But I heard that 255mm fit the 987 front. My own ride (Z4 e89) rides a lot better and is a lot more neutral since I went square (245s). My engine doesn't have that much power and the tires are PSSs so traction works out.

Wimpy tires in the front are just not the way to go.
 

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Discussion Starter #6
I read one guy got fresh tires, and the oversteering went away.

But I am much more aggressive on the front camber and caster, which I think will make the car oversteer prone. The other solution is a front sway, but I'm avoiding that at all costs. It will bump me out of my class. So, the rear sway disconnect is the final solution with new tires.
 

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The issues you want to address are pretty specific, and there are straightforward (if sometimes costly) ways to tackle them head on. You mentioned them in your original post but I think it's worth looking at how they can help your situation.

1. First suggestion is to change to adjustable front and rear sway bars. This is a very direct shot at your stated goals as they will:

  • Reduce roll during cornering, since the replacement bars will be stiffer than the stock ones.
  • Provide a way to directly adjust relative front/rear grip. Too much understeer? Soften the front or stiffen the rear bar. Too much oversteer? Soften the rear or stiffen the front.
  • Added benefit: the tendency to spin the inside rear wheel should be reduced with the reduced body roll.
2. If you want still more traction for powering out of corners, an LSD is the answer. This of course gets expensive fast, and the sway bars on their own should improve things, so it's worth doing them first.

I would personally recommend Tarrett for sway bars - in my experience Ira has been great to work with and stands behind his stuff. You should also think about how important "quiet" is to you, since some of the drop link rod ends can be a bit noisy. There's plenty of info on the forum about different "quiet links" for sway bar ends that will reduce noise.

Best of luck!
 

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Not to revive an old thread, but OP are you having no problems with oil starvation or PS steering leaks/overheating from autox? Most of these issues are coming from guys doing HPDEs but I hear very little from autoxers. Just wondering if the shorter tracks can really do any damage.
 

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Discussion Starter #10
The issues you want to address are pretty specific, and there are straightforward (if sometimes costly) ways to tackle them head on. You mentioned them in your original post but I think it's worth looking at how they can help your situation.

1. First suggestion is to change to adjustable front and rear sway bars. This is a very direct shot at your stated goals as they will:

  • Reduce roll during cornering, since the replacement bars will be stiffer than the stock ones.
  • Provide a way to directly adjust relative front/rear grip. Too much understeer? Soften the front or stiffen the rear bar. Too much oversteer? Soften the rear or stiffen the front.
  • Added benefit: the tendency to spin the inside rear wheel should be reduced with the reduced body roll.
2. If you want still more traction for powering out of corners, an LSD is the answer. This of course gets expensive fast, and the sway bars on their own should improve things, so it's worth doing them first.

I would personally recommend Tarrett for sway bars - in my experience Ira has been great to work with and stands behind his stuff. You should also think about how important "quiet" is to you, since some of the drop link rod ends can be a bit noisy. There's plenty of info on the forum about different "quiet links" for sway bar ends that will reduce noise.

Best of luck!
Thanks for this suggestion. I took your advice, went with the sway bar route. I dropped down a rim size, and stepped up to the RE71R; all without changing classes. The car is very very capable, and I'm consistently placing at the top or near the top of my class.

A quick update, the car is getting some outside rear wear. Potentially just a camber issue. I've been debating what to do, IE: add camber or flip the tires. I'm afraid to mess with the setup mid season. I might just hang on and see where I end up. If I up the rear camber, I should probably follow suit in the front.

Not to revive an old thread, but OP are you having no problems with oil starvation or PS steering leaks/overheating from autox? Most of these issues are coming from guys doing HPDEs but I hear very little from autoxers. Just wondering if the shorter tracks can really do any damage.
No issues with oil starvation. I actually just installed a pressure sender and standalone datalogging unit. On this past event, we had a loop and fast 180 turn. Pressure seemed to stay up just fine. I haven't run into any PS issues either. The car is long over due for a PS fluid change, and I've already got some redline sitting on the shelf waiting.
 

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No issues with oil starvation. I actually just installed a pressure sender and standalone datalogging unit. On this past event, we had a loop and fast 180 turn. Pressure seemed to stay up just fine. I haven't run into any PS issues either. The car is long over due for a PS fluid change, and I've already got some redline sitting on the shelf waiting.
Good to hear! It definitely seems like all the issues are with long constant radius sweepers that don't exist in autox. I'm still new to the CS and P-car family, but is redline's fluid supposed to alleviate some of the PS issues and is it safe to use? I see most saying to stick to Pentosin CHF202.
 

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Discussion Starter #12
Good to hear! It definitely seems like all the issues are with long constant radius sweepers that don't exist in autox. I'm still new to the CS and P-car family, but is redline's fluid supposed to alleviate some of the PS issues and is it safe to use? I see most saying to stick to Pentosin CHF202.
That and the G you can pull based on the tires you have. With my RE71Rs I can pull well over a G in corners at the autox, but they are not very long. If you plan on tracking the car, I'd start with a pressure sender to monitor where the oil pressure is on track.

You have options:
Gauge + pressure sender
Datalogger + pressure sender

If you decide to go with the later, make sure the sender you pick will work with the datalogger or alternatively the datalogger can be configured to properly interpret the sender signals. Some senders are linear, others are not, and you'll need to have this information handy if you go with the datalogger route.

As for the power steering fluid, the pentosin stuff is pretty tasty or at least that is why I hear. At the end of the day it is hydraulic fluid. You can use ATF fluid too. I ultimately selected redline because I think it will handle heat better, but I could be wrong.
 

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I use Pentosin and do 4-5 DEs a yr, including an annual stint at 20-turn COTA. Also have GT3 LCAs and a lot of camber dialed in, which is supposed to be tough on the PS. Never had issues. I do make sure to check the level before every DE w/e. I can't say for sure but I think people have trouble with PS because it takes an effort to check so they don't and go to DEs with the level low. Just a theory but I should have had trouble by now if the PS is such a weak point.
 

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I use Pentosin and do 4-5 DEs a yr, including an annual stint at 20-turn COTA. Also have GT3 LCAs and a lot of camber dialed in, which is supposed to be tough on the PS. Never had issues. I do make sure to check the level before every DE w/e. I can't say for sure but I think people have trouble with PS because it takes an effort to check so they don't and go to DEs with the level low. Just a theory but I should have had trouble by now if the PS is such a weak point.
Are you running a 987.1 or 987.2?

What oiling mods have you done? I've never raced at COTA but was there for MotoGP this yr. Looked like a fun track!
 

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Are you running a 987.1 or 987.2?

What oiling mods have you done? I've never raced at COTA but was there for MotoGP this yr. Looked like a fun track!
987.1 - 2008 Cayman S Sport. I replaced the OEM oil baffle w/ an EBS. Run street tires and shift at 6K rpm.

COTA is a fantastic track with 4 corners > 90deg. Very tough on brakes. My 303hp is a knife at a gun fight w/ all the GT3s, GT4s, TT, etc but still great to drive there.
 

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The best suspension mod I did for AutoX was to install Pedro's TechnoBrace which that ties the bottoms of the rear suspension. The stock bar that was there was a cheap thin aluminum you can flex with your hand. What it is doing is preventing changes in camber during hard turns. Now several other companies sell similar bars, but at a greater price than Perdro's. By the way, it also improved corner steering even on the street. Here's the link: TechnoBrace
 

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Discussion Starter #17
I can't tell from the photos how this bar works.

I'm guessing it ties the subframe together in the rear?
 

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I can't tell from the photos how this bar works.

I'm guessing it ties the subframe together in the rear?
It's a lower struts brace which works to prevent camber change movement by tieing the strut bottoms together while still allowing the struts to function in its up and down design. The Porsche design lower strut bracing is made of flimsy aluminum which flexes under higher camber stress than normal turning. The flex is enough to allow the rear wheel camber to change in mid turn upsetting the handling-ESP in AutoX'ing.

Now some use the upper strut brace, but doesn't really block much of camber movement down below.
 

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Discussion Starter #19
Doesn't the sway bar provide this function too? It is mounted to the bottom of both subframes and ties directly to the rear wheel carrier.
 

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Doesn't the sway bar provide this function too? It is mounted to the bottom of both subframes and ties directly to the rear wheel carrier.
Sway bars function is just an attempt to equalize weight transfer, with the cars design the rear lower struts will still move before the stabilization takes effect. Moreover, even though weight transfer has been minimized, centrifacal force will effect the lower struts movement which is why Porsche used the aluminum plate to minimize that movement.
 
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